It is well known to inject air in the hot water contained in a bathtub to provide a turbulence of the water whereby a user person receives a massaging therapy by the turbulent water. A plurality of orifices are distributed in the side walls of the bathtub in areas where a water massage is required such as in the back wall and lower side wall areas of the bathtub. Various hydro massaging baths are known and such comprise adjustable nozzle assemblies mounted on the wall of a bathtub to discharge high velocity jets of water to impinge upon the body of a user person. However, when injecting air within the hot water, the user person is subjected to a sensation of coolness where the air jets impact its wet body. This sensation is the result of an adiabatic reaction which is caused by air which is relatively dry, and which enters in contact with the water. This sensation is felt even if the air is heated to about 60° C. Increasing the temperature of the air is not the solution to resolve the problem as this would burn a user person's skin. Accordingly, the prior art has opted to mix the air with recirculated water from the bathtub or with heated water such that the injectors comprise a large quantity of water mixed with air.
Another problem of injecting air in the water to cause turbulence is that the air cools the water in the bathtub prematurely because of the large surface contact area of turbulent water with the air. It is therefore desirable to eliminate this cool sensation when injecting air in a bathtub through air injecting orifices or air injectors.
In British Patent GB 2 224 203 published on May 2, 1990, there is disclosed a spa bath in which an air/water mixture is injected via injectors into the water contained within the bath. In that patent, water is taken from the bottom of the bath, heated in a heater and the heated water is supplied to jets within a manifold through which compressed air is blown. The water is injected through venturi orifices which cause water to be sucked through the jets to form fine droplets which are then discharged through the injectors. The droplets of heated water humidify and heat the air immediately before the air/water mixture is injected into the bath, therefore reducing discomfort to the user and maintaining the water temperature in the bath at a desired level. There are several disadvantages of this method, one being that the injector assembly is very expensive and troublesome. In a system as described, it is likely that the injectors will not all operate in a uniform fashion due to variation in pressure along the injector line. The clogging of the venturi gaps due to the fact that the recirculating water entering the nozzles may clog up the nozzles due to the various products and impurities in the water, particularly when water is extracted from the bottom end of the bathtub. Such decalibrates the operation of the injectors. However, this reference confirms that hot bath water is subjected to accelerated cooling when the water is agitated in contact with ambient atmosphere and that unless water is heated to about 50° C., injected air entering the bath will feel cool to a user person's body close to the nozzle creating a “chill effect” caused by blown air in contact with wet skin.